1. Field of the Invention
The present invention relates to an ink jet recording head mounted on an ink jet recording apparatus that performs recording operation by discharging ink.
2. Description of the Related Art
Generally, an ink jet recording head mounted on an ink jet recording apparatus, which performs recording operation by discharging ink, includes a recording element substrate having a discharge port array of a plurality of discharge ports. The recording can be performed at higher speed when the length of the discharge port array is longer.
In such circumstances, in recent years, there has been a growing demand for ink jet recording heads, for example, with a recording width of 4 to 12 inches, which meet the demand for high-speed printing of fine images. However, if a recording element substrate with a long discharge port array is used, the possibility of the problems described below is increased.
Generally, in addition to the discharge port array, a recording element substrate includes recording elements (e.g., electrothermal conversion elements) of a great number that corresponds to the number of the discharge ports. Thus, when the recording elements are arranged on a single recording element substrate, the recording element substrate will be very long. As a result, the possibility of a crack or warpage of the recording element substrate is increased.
Japanese Patent Application Laid-Open No. 2007-296638 discusses an inkjet recording head that can solve such a problem. The inkjet recording head includes a plurality of recording element substrates arranged in an array. According to this configuration, an ink jet recording head of a long recording width is realized without using a single long recording element substrate.
FIG. 18 is a front view of an ink jet recording head with a plurality of recording element substrates according to an exemplary embodiment of the present invention. An ink jet recording head H2000 illustrated in FIG. 18 includes a plurality of recording element substrates H2010, an electric wiring member H2020, and a supporting member H2030.
The recording element substrate H2010 and the electric wiring member H2020 of the ink jet recording head H2000 are secured to the supporting member H2030. Further, as illustrated in FIG. 19, the recording element substrate H2010 is connected to the electric wiring member H2020 by a gold or aluminum wire H1303. FIG. 19 is an enlarged cross-sectional view of an electrical connection portion of the recording element substrate H2010 and the electric wiring member H2020.
The material of the recording element substrate H2010 is silicon, and its coefficient of linear expansion is approximately 3 ppm. The material of the electric wiring member H2020 is resin, and its coefficient of linear expansion is approximately 10 to 30 ppm. The material of the supporting member H2030 is alumina, and its coefficient of linear expansion is approximately 7 ppm.
When a change in temperature occurs due to a recording operation or change in environment, the recording element substrate H2010, the electric wiring member H2020, and the supporting member H2030 of the ink jet recording head H2000 expand/contract in the lengthwise direction of the supporting member H2030 (direction of the arrow A100 in FIG. 20).
At this time, since the coefficient of linear expansion of the electric wiring member H2020 is greater than the coefficient of linear expansion of the recording element substrate H2010, a difference in the amount of expansion/contraction of the components is generated. As a result, the wire H1303 is pulled and the possibility of a breakage of the wire H1303 is increased. If the wire H1303 is broken, the recording element substrate H2010 will not be able to receive electric signals and power and, consequently, ink is not properly discharged. Thus, the breaking of the wire H1303 results in poor image quality.